Coupler array to measure conductor layer misalignment

Abstract

Systems and methods are presented for employing arrays of coupling strips to measure misalignment of layers of multilayer devices as a function of directional coupling between pairs of strips. Each array is capable of detecting misalignment only in the direction perpendicular to the axes of the coupling strips, although multiple arrays may be employed for measuring misalignment in more than one direction. Such arrays are easily manufactured onto existing multilayer devices, and may be excised from such devices after misalignment has been measured.

What is claimed is:  
     
       1. A pair of coupling strips for detecting layer misalignment in a multilayer device, comprising 
       a lower coupling strip formed on a first layer of said multilayer device, and  
       an upper coupling strip formed on a second layer of said multilayer device, the second layer disposed on the first layer so as to be disposed between the lower coupling strip and the upper coupling strip, said upper coupling strip disposed parallel to and offset from the lower coupling strip by a predetermined amount, wherein measuring the amount of coupling in the pair of coupling strips is useful for detection of layer misalignment in the multilayer device.  
     
     
       2. A coupler array in a multilayer device for detecting layer misalignment in the multilayer device, comprising 
       at least two first pairs of coupling strips, wherein each first pair comprises  
       a lower coupling strip formed on a first layer of said multilayer device, and  
       an upper coupling strip formed on a second layer of said multilayer device, the second layer being disposed on the first layer so as to be disposed between the lower coupling strip and the upper coupling strip, the upper coupling strip disposed parallel to and offset from the lower coupling strip by a predetermined amount,  
       wherein the offset amounts of at least two pairs of coupling strips are different, whereby measuring the amount of coupling in different pairs of coupling strips is useful for detection of layer misalignment in the multilayer device.  
     
     
       3. The coupler array of  claim 2 , wherein at least one pair of coupling strips has an offset amount of zero. 
     
     
       4. The coupler array of  claim 2 , wherein the offset amounts of at least two pairs of coupling strips differ by a predetermined amount. 
     
     
       5. The coupler array of  claim 2 , further comprising 
       at least two second pairs of coupling strips disposed in parallel, wherein the offset amounts of at least two second pairs of coupling strips are different, and the second pairs of coupling strips are not parallel to the first pairs of coupling strips.  
     
     
       6. The coupler array of  claim 5 , wherein measuring the amount of coupling in first pairs of coupling strips and in second pairs of coupling strips is useful for determining layer misalignment in two dimensions. 
     
     
       7. The coupler array of  claim 2 , further comprising 
       at least two second pairs of coupling strips disposed in parallel, wherein the offset amounts of at least two second pairs of coupling strips differ, and wherein the upper coupling strips of said second pairs of coupling strips are disposed on a third layer of said multilayer device, and the lower coupling strips of said second pairs of coupling strips are disposed on the second layer of said multilayer device, the third layer being disposed on the second layer so as to be disposed between the lower coupling strips and the upper coupling strips of said second pairs of coupling strips.  
     
     
       8. A method for detecting misalignment of layers in a multilayer device, comprising 
       providing a device including a coupler array of  claim 2 ,  
       measuring amounts of coupling in at least two pairs of coupling strips,  
       comparing the amounts of coupling measured in different pairs of coupling strips, and  
       determining the relative alignment of the first layer with the second layer.  
     
     
       9. A system for measuring misalignment of layers in a multilayer device, comprising 
       a coupler array of  claim 2 ,  
       a microwave generator coupled to at least one pair of coupling strips, and  
       a microwave receiver to measure the amount of coupling in the at least one pair of coupling strips.  
     
     
       10. A method for measuring misalignment of layers in a multilayer device, comprising the acts of 
       providing a coupler array according to  claim 2 ,  
       providing a microwave generator,  
       coupling said generator to a first pair of coupling strips,  
       measuring the amount of coupling in the first pair of coupling strips,  
       coupling said generator to a second pair of coupling strips,  
       measuring the amount of coupling in the second pair of coupling strips,  
       comparing the amount of coupling in the first pair of coupling strips to the amount of coupling in the second pair of coupling strips, and  
       determining the misalignment of layers in the multilayer device.  
     
     
       11. A method for manufacturing a pair of coupling strips for detecting layer misalignment in a multilayer device, comprising the acts of 
       providing a first layer of said multilayer device,  
       forming a lower coupling strip on the first layer of said multilayer device,  
       disposing a second layer of said multilayer device above said lower coupling strip, and  
       forming an upper coupling strip on the second layer of said multilayer device, said upper coupling strip being separated a distance apart from the lower coupling strip, disposed parallel to the lower coupling strip and offset from the lower coupling strip by an offset amount.  
     
     
       12. A method for manufacturing a coupler array for detecting layer misalignment, comprising the acts of 
       providing a first layer of said multilayer device,  
       forming at least two lower coupling strips on the first layer of said multilayer device,  
       disposing a second layer of said multilayer device above said lower coupling strips, and  
       disposing at least two corresponding upper coupling strips on the second layer of said multilayer device, wherein lower coupling strips and corresponding upper coupling strips form pairs of coupling strips,  
       wherein, for each pair of coupling strips, said upper coupling strip is disposed parallel to said lower coupling strip and offset from the lower coupling strip by an offset amount whereby at least two pairs of coupling strips have different offset amounts.  
     
     
       13. The method of  claim 12 , wherein the act of disposing includes disposing at least one pair of coupling strips having an offset amount of zero. 
     
     
       14. The method of  claim 12 , wherein the act of disposing includes disposing at least two pairs of coupling strips having predetermined offset amounts. 
     
     
       15. A method for detecting misalignment of layers in a multilayer device, comprising 
       providing a device having a first layer including at least two first reference probes disposed parallel to each other and spaced by a predetermined amount and a second layer including at least two second reference probes disposed parallel to each other, spaced by a different predetermined amount, the second layer disposed on the first layer so as to be disposed between the first reference probes and the second reference probes,  
       measuring an amount of coupling between at least two said first reference probes and corresponding second reference probes,  
       comparing the amounts of coupling measured for different reference probes, and  
       determining the misalignment of the first layer with the second layer.